Two-Dimensional (001) LaAlO₃/SrTiO₃ Heterostructures with Adjustable Band Gap and Magnetic Properties

Very recently, freestanding crystalline perovskite films as thin as a single unit cell have been successfully synthesized, which expands the opportunities for research and applications of low-dimensional materials with novel functionalities. In this work, we constructed a series of two-dimensional (2D) (001) LaAlO₃/SrTiO₃ heterostructures and systematically investigated their atomic and electronic properties by means of first-principles calculations. Our results show that (1) nonstoichiometry leads to ferromagnetism at the interfaces of the systems; (2) half-metallicity can be realized by introducing slight hole-doping; and (3) a semiconductor-to-metal transition can be triggered by applying a moderate (within 3%) out-of-plane strain. Besides, based on in-depth analysis of the electronic structures, we propose that the orbital hybridization of interfacial O and Ti atoms may play a crucial role in determining the above interesting phenomena. Our findings are expected to stimulate further experimental researches on the related 2D perovskite heterostructures and to be beneficial for the design of new multifunctional electronic devices.